Patent GB-953152-A (GB)
Title: Improvements relating to fluorine-containing elastomeric copolymers
IPC: C08F16/12
Filed: 1962-06-20
Abstract: 2-(Perflouroalkoxy) perfluoropropionic acid fluorides may be prepared by reacting carbonyl fluoride or a perfluorinated acid fluoride with hexafluoropropylene oxide in the presence of a catalyst, e.g. activated carbon, alkali metal fluorides, silver fluoride or quaternary ammonium flourides, in the presence of a polar solvent, e.g. acetonitrile, benzonitrile, dialkyl ethers of ethylene glycol and diethylene glycol, N-methyl-2-pyrrolidone and dimethyl sulphonide. The products may be converted to alkali metal salts by treating with alkali metal hydroxides, and the salts may be pyrolysed dry or in the presence of a polar solvent, e.g. 1,2-dimethoxyethane or benzonitrile, to rield perfluoroalkyl perfluorovinyl ethers. In example 5 2-(perfluoromethoxy) perfluoropropionyl fluoride is prepared by reacting carbonyl fluoride with hexafluoropropylene oxide in the presence of caesium fluoride and diethylene glycol dimethyl ether. In Example 6 the acid fluoride is converted to the potassium salt by treating with potassium hydroxide and the salt pyrolysed to give perfluoromethyl perfluorovinyl ether.ALSO:Elastomeric copolymers comprising 83 to 25% mol. of vinylidene fluoride units and 17 to 75% mol. of perfluoroalkyl perfluorovinyl ether units in which the perfluoroalkyl group contains 1 to 3 carbon atoms may be prepared by copolymerizing the monomers with the aid of a free radical polymerization initiator in the absence of oxygen.  The polymerization may be effected in bulk or in the presence of a liquid medium, e.g. water which may contain emulsifying agents such as ammonium perfluorocaprylate and ammonium o -hydroperfluoroheptanoate, or perfluorinated solvents such as perfluorodimethylcyclohexane. Specified initiators are hydrogen peroxide, benzoyl peroxide, cumene hydroperoxide, sodium persulphate, potassium persulphate, ammonium persulphate, nitrogen fluorides and 2,21-azobis-(2-methyllpropionitrile). Polymerization may be effected in the presence of a chain transfer agent, e.g. n-hexane, carbon tetrachloride, acetone or ethyl acetate.  The elastomeric copolymers may be compounded and cured with conventional ingredients and agents, e.g. carbon black, silica, pigments, zinc oxide, magnesium oxide, hexamethylenediamine carbamate, benzoyl peroxide, N,N1-bis(arylalkylidene) alkylenediamines, aliphatic and cycloaliphatic diamines, organic dimercaptans in conjunction with aliphatic tertiary amines and high energy radiation.  The products may be used in making O-rings, packings, seals, diaphragms, hose, electrical insulation and protective coatings. Low molecular weight copolymers may be used as heat-resistant plasticizers for solid fluorocarbon elastomers. Examples describe the copolymerization in aqueous emulsion in the presence of ammonium persulphate and ammonium perfluorocaprylate of (1, 2 and 4) vinylidene fluoride and perfluoromethyl perfluorovinyl ether and (3) vinylidene fluoride and perfluoropropyl perfluorovinyl ether; and the copolymerization in bulk in the presence of nitrogen difluoride of (7) vinylidene fluoride and perfluoromethyl perfluorovinyl ether.